Why did senators oppose the idea of Julius Caesar becoming the leader after Crassus died?

The opposition of some Roman senators to Julius Caesar's leadership after the death of Crassus can be attributed to a number of factors. Crassus was part of the First Triumvirate, a political alliance including Julius Caesar, Crassus, and Pompey. The alliance was unofficial but powerful, and it helped the three men to dominate the Roman political landscape.

1. Threat to the Republic: Some senators feared that Caesar's increasing power represented a threat to the Roman Republic. This was a time when strong political figures often attempted to usurp power, and the balance of the Republic was delicate.

2. Political Rivalry: Caesar had numerous political rivals in the Senate. The Senate was the traditional seat of power in Rome, and many senators were unsettled by the rise of individual military leaders like Caesar.

3. Fear of Monarchy: Caesar's successes in Gaul and his increasing popularity with the army and the masses made him appear as a potential monarch or dictator. Senators, particularly those favoring the traditional republican system of governance, were very concerned that Caesar's ascent could lead to a monarchy, which the Republic had been founded to avoid.

4. Loss of Power and Privilege: Senators, many of whom were from noble families and thus part of the patrician class, were worried about losing their power and privileges. Caesar's populist tendencies and reforms threatened their economic benefits and influence.

5. Personal Enmities: Personal rivalries and the politics of envy could have also played a role. Caesar was known for his ambition and lack of respect for some of the established norms, which made him unpopular with some senators.

6. Legal Concerns: When Crassus died, Caesar was still commanding his army in Gaul. Roman law at the time dictated that he should have disbanded his army and returned to Rome as a private citizen before holding any further office. His reluctance to do so without guarantees of safety and immunity from prosecution was a clear point of contention.

Following Crassus's death, the balance of power within the Triumvirate was destabilized, and Pompey aligned himself more closely with the Senate. Caesar's powerful position and ambition made him a focal point for those who were wary of the potential for a single individual to overthrow the Republican system.